The invention disclosed herein relates to an apparatus and methods for producing disposable products such as diapers at very high speeds. While the description provided relates to diaper manufacturing, the apparatus and method are easily adaptable to other applications. In particular this invention relates to an apparatus for turning and placing either portions of or discrete disposable products such as diapers.
Generally, diapers comprise an absorbent insert or patch and a chassis, which, when the diaper is worn, supports the insert proximate a wearer's body. Additionally, diapers may include other various patches, such as tape tab patches, reusable fasteners and the like. The raw materials used in forming a representative insert are typically cellulose pulp, tissue paper, poly, nonwoven web, acquisition, and elastic, although application specific materials are sometimes utilized. Usually, most of the insert raw materials are provided in roll form, and unwound and applied in continuously fed fashion.
In the creation of a diaper, multiple roll-fed web processes are typically utilized. To create an absorbent insert, the cellulose pulp is unwound from the provided raw material roll and de-bonded by a pulp mill. Discrete pulp cores are created using a vacuum forming assembly and placed on a continuous tissue web. Optionally, super-absorbent powder may be added to the pulp core. The tissue web is wrapped around the pulp core. The wrapped core is debulked by proceeding through a calendar unit, which at least partially compresses the core, thereby increasing its density and structural integrity. After debulking, the tissue-wrapped core is passed through a segregation or knife unit, where individual wrapped cores are cut. The cut cores are conveyed, at the proper pitch, or spacing, to a boundary compression unit.
While the insert cores are being formed, other insert components are being prepared to be presented to the boundary compression unit. For instance, the poly sheet is prepared to receive a cut core. Like the cellulose pulp, poly sheet material is usually provided in roll form. The poly sheet is fed through a splicer and accumulator, coated with an adhesive in a predetermined pattern, and then presented to the boundary compression unit. In addition to the poly sheet, which may form the bottom of the insert, a two-ply top sheet may also be formed in parallel to the core formation. Representative plies are an acquisition layer web material and a nonwoven web material, both of which are fed from material parent rolls, through a splicer and accumulator. The plies are coated with adhesive, adhered together, cut to size, and presented to the boundary compression unit. Therefore, at the boundary compression unit, three components are provided for assembly: the poly bottom sheet, the core, and the two-ply top sheet.
A representative boundary compression unit includes a profiled die roller and a smooth platen roller. When all three insert components are provided to the boundary compression unit, the nip of the rollers properly compresses the boundary of the insert. Thus, provided at the output of the boundary compression unit is a string of interconnected diaper inserts. The diaper inserts are then separated by an insert knife assembly and properly oriented, such as disclosed in co-pending U.S. Application No. 61/426,891, owned by the assignee of the present invention and incorporated herein by reference. At this point, the completed insert is ready for placement on a diaper chassis.
A representative diaper chassis comprises nonwoven web material and support structure. The diaper support structure is generally elastic and may include leg elastic, waistband elastic and belly band elastic. The support structure is usually sandwiched between layers of the nonwoven web material, which is fed from material rolls, through splicers and accumulators. The chassis may also be provided with several patches, besides the absorbent insert. Representative patches include adhesive tape tabs and resealable closures.
The process utilizes two main carrier webs; a nonwoven web which forms an inner liner web, and an outer web that forms an outwardly facing layer in the finished diaper. In a representative chassis process, the nonwoven web is slit at a slitter station by rotary knives along three lines, thereby forming four webs. One of the lines is on approximately the centerline of the web and the other two lines are parallel to and spaced a short distance from the centerline. The effect of such slitting is twofold; first, to separate the nonwoven web into two inner diaper liners. One liner will become the inside of the front of the diaper, and the second liner will become the inside of the back of that garment. Second, two separate, relatively narrow strips are formed that may be subsequently used to cover and entrap portions of the leg-hole elastics. The strips can be separated physically by an angularly disposed spreader roll and aligned laterally with their downstream target positions on the inner edges of the formed liners. This is also done with turn bars upon entrance to the process.
After the nonwoven web is slit, an adhesive is applied to the liners in a predetermined pattern in preparation to receive leg-hole elastic. The leg-hole elastic is applied to the liners and then covered with the narrow strips previously separated from the nonwoven web. Adhesive is applied to the outer web, which is then combined with the assembled inner webs having elastic thereon, thereby forming the diaper chassis. Next, after the elastic members have been sandwiched between the inner and outer webs, an adhesive is applied to the chassis. The chassis is now ready to receive an insert.
In diapers it is preferable to contain elastics around the leg region in a cuff to contain exudates for securely within the diaper. Typically, strands of elastic are held by a non-woven layer that is folded over itself and contains the elastics within the overlap of the non-woven material. The non-woven is typically folded by use of a plow system which captures the elastics within a pocket, which is then sealed to ensure that the elastics remain in the cuff.
Most products require some longitudinal folding. It can be combined with elastic strands to make a cuff. It can be used to overwrap a stiff edge to soften the feel of the product. It can also be used to convert the final product into a smaller form to improve the packaging.
To assemble the final diaper product, the Insert must be combined with the chassis. The placement of the insert onto the chassis occurs on a placement drum or at a patch applicator. The inserts are provided to the chassis on the placement drum at a desired pitch or spacing. The generally flat chassis/insert combination is then folded so that the inner webs face each other, and the combination is trimmed. A sealer bonds the webs at appropriate locations prior to individual diapers being cut from the folded and sealed webs.
Roll-fed web processes typically use splicers and accumulators to assist in providing continuous webs during web processing operations. A first web is fed from a supply wheel (the expiring roll) into the manufacturing process. As the material from the expiring roll is depleted, it is necessary to splice the leading edge of a second web from a standby roll to the first web on the expiring roll in a manner that will not cause interruption of the web supply to a web consuming or utilizing device.
In a splicing system, a web accumulation dancer system may be employed, in which an accumulator collects a substantial length of the first web. By using an accumulator, the material being fed into the process can continue, yet the trailing end of the material can be stopped or slowed for a short time interval so that it can be spliced to leading edge of the new supply roll. The leading portion of the expiring roll remains supplied continuously to the web-utilizing device. The accumulator continues to feed the web utilization process while the expiring roll is stopped and the new web on a standby roll can be spliced to the end of the expiring roll.
In this manner, the device has a constant web supply being paid out from the accumulator, while the stopped web material in the accumulator can be spliced to the standby roll. Examples of web accumulators include that disclosed in U.S. patent application Ser. No. 11/110,616, which is commonly owned by the assignee of the present application, and incorporated herein by reference.
As in many manufacturing operations, waste minimization is a goal in web processing applications, as products having spliced raw materials cannot be sold to consumers. Indeed, due to the rate at which web processing machines run, even minimal waste can cause inefficiencies of scale. In present systems, waste materials are recycled. However, the act of harvesting recyclable materials from defective product is intensive. That is, recyclable materials are harvested only after an identification of a reject product at or near the end of a process. The result is that recyclable materials are commingled, and harvesting requires the extra step of separating waste components. Therefore, the art of web processing would benefit from systems and methods that identify potentially defective product prior to product assembly, thereby eliminating effort during recyclable material harvesting.
Furthermore, to improve quality and production levels by eliminating some potentially defective product, the art of web processing would benefit from systems and methods that ensure higher product yield and less machine downtime.
Some diaper forming techniques are disclosed in co-pending U.S. application Ser. No. 12/925,033 which is incorporated herein by reference. As described therein, a process wherein a rotary knife or die, with one or more cutting edges, turns against and in coordination with a corresponding cylinder to create preferably trapezoidal ears. Ear material is slit into two lanes, one for a left side of a diaper and the other for a right side of a diaper. Fastening tapes are applied to both the right and the left ear webs. The ear material is then die cut with a nested pattern on a synchronized vacuum anvil.
The resulting discrete ear pieces however, due to the trapezoidal pattern of the ears, alternate between a correct orientation and an incorrect (reversed) orientation. The reversed ear is required to be rotated 180° into the correct orientation such that the ears and associated tape present a left ear and a right ear on the diaper.
To accomplish the reversal of the ear pattern, discrete ear pieces are picked up at the nested ear pitch by an ear turner assembly that will expand to a pitch large enough for ears to be unnested and allow clearance for every other ear to be rotated. The rotated ears are then unnested and into the correct orientation.
Two ear turner assemblies can be provided, to rotate every other ear applied to the right side of the product, and every other ear applied to the left side of the product. In this manner, for a single product, one of the two ears will have been rotated 180°.
Ear application to a chassis web can be by a bump method with intermittent adhesive applied to the chassis web, or can be by vacuum transfer.
Two side panel assemblies, including fastening mechanisms, can be attached to two ears, the side panel assemblies attached in a pre-folded condition. Two more ears can coupled to a chassis web to create a front panel to wear about the waist of a user.
Chips of material can also be removed from the ears to provide a diaper with contoured leg openings. In one embodiment, the chips may be removed from the ears before the ears are attached to the chassis web. In an additional embodiment the chips may be removed from the ears after the ears are attached to the chassis web. In an additional embodiment the chips may be removed from the ears and a portion of the chassis web removed after the ears are attached to the chassis web.
Generally, diapers comprise an absorbent insert or patch and a chassis, which, when the diaper is worn, supports the insert proximate a wearer's body. Additionally, diapers may include other various patches, such as tape tab patches, reusable fasteners and the like. The raw materials used in forming a representative insert are typically cellulose pulp, tissue paper, poly, nonwoven web, acquisition, and elastic, although application specific materials are sometimes utilized. Usually, most of the insert raw materials are provided in roll form, and unwound and applied in assembly line fashion. As in many manufacturing operations, waste minimization is a goal in web processing applications, as products having spliced raw materials cannot be sold to consumers. Indeed, due to the rate at which web processing machines run, even minimal waste can cause inefficiencies of scale.
In present systems, waste materials are recycled. However, the act of harvesting recyclable materials from defective product is intensive. That is, recyclable materials are harvested only after an identification of a reject product at or near the end of a process. The result is that recyclable materials are commingled, and harvesting requires the extra step of separating waste components. Therefore, it is beneficial to use up all of incoming rolls, so that a portion of the incoming rolls do not become waste. That objective is accomplished with the present invention
When manufacturing hygiene products, such as baby diapers, adult diapers, disposable undergarments, incontinence devices, sanitary napkins and the like, a common method of applying discrete pieces of one web to another is by use of a slip-and-cut applicator. A slip-and-cut applicator is typically comprised of a cylindrical rotating vacuum anvil, a rotating knife roll, and a transfer device. In typical applications, an incoming web is fed at a relatively low speed along the vacuum face of the rotating anvil, which is moving at a relatively higher surface speed and upon which the incoming web is allowed to “slip”. A knife-edge, mounted on the rotating knife roll, cuts a off a segment of the incoming web against the anvil face. This knife-edge is preferably moving at a surface velocity similar to that of the anvil's surface. Once cut, the web segment is held by vacuum drawn through holes on the anvil's face as it is carried at the anvil's speed downstream to the transfer point where the web segment is transferred to the traveling web.
Continual improvements and competitive pressures have incrementally increased the operational speeds of disposable diaper converters. As speeds increased, the mechanical integrity and operational capabilities of the applicators had to be improved accordingly.
In some instances, disposable products manufacturers choose to use pre-formed stretched laminate to construct products such as diapers. In a typical diaper, it is preferred to have a stretch from side to side across the waist of a user. In prior art diaper construction techniques, machines are used that construct stretch laminates in a machine direction, and then rotate the stretch laminates to receive an absorbent core roughly perpendicular to the front and rear panels. However, if the pre-formed stretched laminate is supplied with the stretch perpendicularly to the unwind or machine direction, the prior art machines would not orient the stretch characteristics of the front and rear or back panels properly. Therefore, a machine is necessary to fabricate diapers from an unwind roll that presents the stretch direction perpendicular to the machine direction.